The present invention relates to a method of preparing a modified syndiotactic polystyrene with polarity by modifying syndiotactic polystyrene with non-polarity with a monomer component with polarity. More particularly, the present invention relates to a method of preparing a modified syndiotactic polystyrene with polarity by swelling syndiotactic polystyrene with non-polarity in a batch reactor and grafting monomers having a polar group such as maleic anhydride onto the swollen syndiotactic polystyrene.
Syndiotactic polystyrene (sPS) was first synthesized in 1985, using a homogeneous organometallic catalytic system based on a titanium compound and methylaluminoxane (N. Ishihara, T. Seimiya, M. Kuramoto and M. Uoi, Macromolecules 1986, 19, 2465).
Syndiotactic polystyrene has low specific gravity, low dielectric constant, high modulus of elasticity and excellent resistance to chemicals. Accordingly the syndiotactic polystyrene has become a promising engineering plastic material for various applications in the electronic and packaging industries. However, syndiotactic polystyrene has disadvantageously low compatibility with other polymers, poor adhesive strength with a metal component and low impact strength. In order to solve these problems, there has been proposed methods of polarizing syndiotactic polystyrene itself or copolymerizing sPS with a polymer having a polar group.
The method of modifying by polarizing atactic polystyrene have been studied for a long time, and there are many research reports on this subject. Modified copolymers such as acrylonitrile/butadiene/styrene (ABS) or styrene/butadiene/styrene (SBS) by the use of radical can be prepared by graft copolymerization, especially in butadiene region of the polymer (J. A. Chandrasiri and C. A. Wilkie, J. Polym. Sci. Part A: polymer Chem., 1996, 34, 1113).
Xue and Wilkie discloses that the graft-copolymerization of acrylonitrile onto polystyrene by a radical process cannot occur, because the methine hydrogen may not be removed by radicals (T. J. Xue and C A. Wilkie, J. Polym. Sci. Part A: polymer Chem., 1997, 35, 1275). In addition, the solution process does not permit successful graft copolymerization due to its low productivity and complexity of the solvent post-treating process. Furthermore, modification reaction cannot occur in a solution state (T. J. Xue and C A. Wilkie, J. Polym. Sci. Part A: polymer Chem., 1997, 35, 1275).
Atactic polystyrenes which exhibit no stereoregularity can not produce any efficient blend without use of a styrenic copolymer such as SBS, SEBS, SIS or SEP. For instance, styrene-co-maleic anhydride (SMA), which is a copolymer of atactic polystyrene with maleic anhydride, has poor processability at high temperature since maleic anhydride is copolymerized irregularly with the main chain of polystyrene. Any research on modifying syndiotactic polystyrene processed at high temperature has not been conducted sufficiently.
Idemitsu Kosan Company of Japan proves that 3 mol % and more of alkyl styrene such as methyl styrene leads to a graft copolymerization (U.S. Pat. No. 5,760,105). However, the study of directly copolymerizing syndiotactic polystyrene with maleic anhydride has not obtained satisfactory results yet, since it employs syndiotactic poly(styrene-methylstyrene) copolymer as a stating material, which requires a further polymerization step.
Until now, there have been no experiments or results about introduction of a polar group such as maleic anhydride to syndiotactic polystyrene directly. Therefore, the present inventors have developed the method of introducing a polar group such as maleic anhydride to syndiotactic polystyrene directly.
In general, methods of introduction of maleic anhydride to polyolefin or a copolymer such as ABS and SEBS are known well, for example, a solution process, which comprises preparing a solution of starting polymer with a certain solvent and introducing a polar group into the solution. However, this method gives rise to difficulty in applying to syndiotactic polystyrene. That is, solvent for dissolving syndiotactic polystyrene has a high boiling point, which causes difficulty in process control and solvent post-treating process, resulting in disadvantages in large-scale production.
Accordingly, the present inventors have developed a method for preparing a modified syndiotactic polystyrene with polarity by use of syndiotactic polystyrene in the form of powder as a staring material in a batch process instead of a solution process and by using a slurry process in which the starting material is swelled with solvent.
It is an object of the present invention to provide a novel method of preparing a modified syndiotactic polystyrene using syndiotactic polystyrene in the form of powder compared to a conventional method using atactic polystyrene.
It is another object of the present invention to provide a method of preparing a modified syndiotactic polystyrene having good compatibility with other materials, which is characterized by slurrying syndiotactic polystyrene in the form of powder to induce graft polymerization.
It is still another object of the present invention to provide a method of preparing a modified syndiotactic polystyrene having good impact strength.
It is still another object of the present invention to provide a method of preparing a modified syndiotactic polystyrene without limitation of the scope of this application.
It is still another object of the present invention to provide a method of preparing a modified syndiotactic polystyrene which is easy for handling and prevents deterioration and oxidation by conducting the reaction in a slurry state by use of syndiotactic polystyrene as a starting material at low temperature.
It is still another object of the present invention to provide a method of preparing a modified syndiotactic polystyrene which can rule out circumstantial effects such as a temperature.
It is still another object of the present invention to provide a method of preparing a modified syndiotactic polystyrene without deterioration of properties such as thermal property by conducting the graft reaction in an amorphous section of syndiotactic polystyrene after forming swollen syndiotactic polystyrene.
The above and other objects and advantages of this invention will be apparent from the ensuing disclosure and appended claims.